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Posted: July 24, 2008

Nanotechnology may aid PCa diagnosis

(Nanowerk News) Once limited to the electronics industry, semiconductor material may hold the key to improving early detection of prostate cancer among African-American men.

Nanotechnology using quantum dots (QD) made from semiconductor material allowed researchers to detect six biomarkers linked to prostate cancer. Quantum dots (QD) are 5-20 nm in diameter. For comparison, a human hair measures 100,000 nm in diameter. The small size of the QDs results in new optical properties that allow observers to determine the size and energy of the QD and where it will emit light along the color spectrum.

“Smaller QDs are higher energy and emit in the blue part of the spectrum, whereas the larger-sized but lower-energy QDs emit light in the red part of the spectrum,” explained lead in-vestigator Catherine Phelan, MD, PhD, an assistant professor in cancer prevention and control at H. Lee Moffitt Cancer Center & Research Institute, Tampa, Fla. “If you want to look at a particular known protein in the blood, such as PSA, you can attach the specific antibody for that protein to the QD and, using a laser, observe where the emission peak lies in the color spectrum. The height of the peak represents the amount of protein in the blood sample.”

The researchers observed that the bioconjugated QDs displayed a spectral shift in comparison with nonconjugated QDs. The researchers found that the shift is different for each antibody-QD pair and thus different antibodies show a peak at different wavelengths. Dr. Phelan said there are two main advantages to QD technology for measuring blood proteins over current methods. First, the optical properties of QDs allow protein detection at much lower levels when the tumor is in its earliest stages. Second, the technology enables detection of multiple biomarkers simultaneously, thus increasing the specificity for detecting cancer versus non-cancer.

“This novel technology can be used for detection of any cancer in any ethnic group,” said Dr. Phelan, who presented findings here at the American Association for Cancer Research annual meeting.

The biomarkers in the study are not unique to African-American men with prostate cancer, but the baseline levels of the proteins may differ among ethnic groups. She said the technology could also be used to detect risk of recurrence, although the biomarkers may be different than for early detection.

African-American men have the highest incidence and mortality from prostate cancer in the world. Five-year survival rates are almost 100% for African-American men diagnosed with early-stage prostate cancer but only 29% for African-American men diagnosed in the late stages of the disease.

Dr. Phelan and her colleagues are investigating nanotechnologies to enhance the detection of prostate cancer biomarkers at extremely low serum levels. The goal is to engineer a multi-biomarker panel that will provide sufficiently high sensitivity and specificity such that it can be applied as a screening test. Their ultimate goal is to decrease prostate cancer morbidity and mortality among African-American men.

“We are trying to use this technology to detect cancer very early. I would hope that this would eventually become an assay that doctors could use and it could become widely available. This was a small study and we need to validate it,” Dr. Phelan told Renal & Urology News.